Design Files & Part List

The emonTx Shield schematic and board design, in Eagle CAD format, can be viewed and downloaded from the emonTx Shield GitHub page.

Build Guide

Follow the component labels on the PCB using the part list above to identify the components, and the completed build photo below, to double check correct component placement. If you are going to use a current transformer with an internal burden resistor (e.g. the YHDC SCT-013-030 or another "voltage output" type), do not fit the 33 Ω resistor for that input channel:

Hardware Setup Instructions

On the top of the board, there are two solder jumpers (older boards only) which need to be connected before the emonTx Shield can operate. On later boards, these have been replaced by header pins and jumper links.

RFM12B / RFM69CW Slave Select (SS) Solder Jumper Setting

The left hand solder jumper determines which Arduino digital I/O is used for the RFM SS pin. Digital 10 is the JeeLib library default. For standard operation, connect the solder jumper to 10 by connecting the middle pad to the left pad shown in this image.

However if Digital 10 is required by another shield (e.g Arduino Ethernet) another free digital pin can be used as the RFM SS pin. There are two options available. The first option requires hardware modification, the second requires software modification. We recommend the first option:

Option 1

Ensure the RFM12B SS pin solder jumper is not connected (middle pad not soldered to either left or right pads).

Solder a wire from the middle pad to either Digital 8 or 9. There is a hole available for this, see the image above.

RFM12B / RFM69CW Interrupt Solder Jumper Setting

The right hand solder jumper sets the RFM12B interrupt pin. The setting of this jumper depends on which Arduino board the shield is connected to. Connect the jumper to Digital 2 for Arduino Uno/Duemilanove or Digital 3 for Arduino Leonardo. These pins connect to the special hardware interrupt pin INT0.

Arduino Compatibility

Arduino clones that have on-board Ethernet (e.g. at least one of the Australian-made Freetronics boards) and some Ethernet Shields appear to use Analog I/O for purposes connected with the Ethernet controller. This is not compatible with the use of the analogue input(s) for voltage or current measurements. On the Freetronics unit, it appears there are pull-up resistors for the MAC address chip attached to A4 and A5 that can be disconnected by cutting track jumpers to disable MAC addressing, but enable use of CT 4 input for current measurements.
More details can be found here:
freetronics forum and
OpenEnergyMonitor forum